libostree

This project is now known as "libostree", though it is still appropriate to use
the previous name: "OSTree" (or "ostree"). The focus is on projects which use
libostree's shared library, rather than users directly invoking the command line
tools (except for build systems). However, in most of the rest of the
documentation, we will use the term "OSTree", since it's slightly shorter, and
changing all documentation at once is impractical. We expect to transition to
the new name over time.

As implied above, libostree is both a shared library and suite of command line
tools that combines a "git-like" model for committing and downloading bootable
filesystem trees, along with a layer for deploying them and managing the
bootloader configuration.

The core OSTree model is like git in that it checksums individual files and has
a content-addressed-object store. It's unlike git in that it "checks out" the
files via hardlinks, and they thus need to be immutable to prevent corruption.
Therefore, another way to think of OSTree is that it's just a more polished
version of
Linux VServer hardlinks.

Projects using OSTree

rpm-ostree is a next-generation
hybrid package/image system for Fedora and CentOS,
used by the Atomic Host project.
By default it uses libostree to atomically replicate a base OS (all dependency
resolution is done on the server), but it supports "package layering", where
additional RPMs can be layered on top of the base. This brings a "best of both worlds""
model for image and package systems.

flatpak uses libostree for desktop
application containers. Unlike most of the other systems here, flatpak does not
use the "libostree host system" aspects (e.g. bootloader management), just the
"git-like hardlink dedup". For example, flatpak supports a per-user OSTree
repository.

GNOME Continuous is
where OSTree was born - as a high performance continuous delivery/testing
system for GNOME.

The BuildStream build and
integration tool uses libostree as a caching system to store and share
built artifacts.

Language bindings

libostree is accessible via GObject Introspection;
any language which has implemented the GI binding model should work.
For example, Both pygobject
and gjs are known to work
and further are actually used in libostree's test suite today.

Some bindings take the approach of using GI as a lower level and
write higher level manual bindings on top; this is more common
for statically compiled languages. Here's a list of such bindings:

Building

Releases are available as GPG signed git tags, and most recent
versions support extended validation using
git-evtag.

However, in order to build from a git clone, you must update the
submodules. If you're packaging OSTree and want a tarball, I
recommend using a "recursive git archive" script. There are several
available online;
this code
in OSTree is an example.

Once you have a git clone or recursive archive, building is the
same as almost every autotools project:

More documentation

Contributing

Licensing

The licensing for the code of libostree can be canonically found in the individual files;
and the overall status in the COPYING
file in the source. Currently, that's LGPLv2+. This also covers the man pages and API docs.

The license for the manual documentation in the doc/ directory is:
SPDX-License-Identifier: (CC-BY-SA-3.0 OR GFDL-1.3-or-later)
This is intended to allow use by Wikipedia and other projects.

In general, files should have a SPDX-License-Identifier and that is canonical.